This project will complete development efforts toward commercialization of multilineage point-of-care Lassa fever diagnostics. Lassa fever (LF) is a severe, often fatal viral hemorrhagic fever (VHF). Because of its high case fatality rate, ability o spread easily by human-human contact, and potential for aerosol release, Lassa virus (LASV), the causative agent of Lassa fever, is classified as a Biosafety Level 4 and NIAID Biodefense category A agent. Our team has successfully produced, validated, CE marked and commercialized recombinant LASV point-of-care lateral flow immunodiagnostics (LFI) for rapid diagnosis of LF caused by lineage IV virus strains. These assays are based on recombinant proteins rather than on reagents that must be produced in high containment laboratories. We have also established robust research programs in Sierra Leone and Nigeria, both endemic areas for LASV, that provide unique clinical and laboratory resources for VHF research. The recombinant immunoassays developed for strains of LASV prevalent in Sierra Leone and surrounding countries will now be reconfigured for the three divergent lineages of LASV in Nigeria - due to lack of sensitivity of lineage IV-specific RDTs for circulating viruses from lineages I-III arising from strain variation. We will now perform critical steps in late-stage development toward commercialization of multilineage point-of- care LF diagnostics. In MILESTONE 1 we will complete development of commercial grade LASV antigen- capture and immunoglobulin M (IgM) and immunoglobulin G (IgG) antibody-capture enzyme-linked immunosorbent assays (ELISA) to lineage I-IV LASV using a Developmental Panel of well-characterized sera. In MILESTONE 2 we will complete development of LASV multilineage LFI as point-of-care diagnostics using the Developmental Serum Panel and newly developed antibodies. In MILESTONE 3 we will convert to manufacturing multilineage recombinant ELISA and LFI under Good Manufacturing Procedures (GMP) to provide quantities of commercial grade diagnostic kits sufficient for preclinical evaluation of design control parameters to achieve benchmarks required for clinical studies, CE marking, and commercialization. In MILESTONE 4 we will optimize scale up and purification of recombinant LASV nucleoprotein (NP) representing currently circulating LASV lineages I-IV, and scale up/purification methods for antibodies to recombinant LASV NP recognizing all currently circulating LASV lineages I-IV. We will then transfer to manufacturing to provide quantities of recombinant proteins and antibodies sufficient for development and production of commercial assays. In MILESTONE 5 we will define and collect positive and negative sera for assay validation from diverse regions across the LASV endemic range of West Africa and elsewhere (European and U.S. controls). We will then validate sensitivity and specificity of multilineage LF recombinant ELISA and LFI. In MILESTONE 6 we will compile Design Validation Report for multilineage reLASV RDT, submission to European Commission for CE marking and to NAFDAC for product registration in Nigeria.